Early attempts to generate the trifluoromethide ion (CF.sub.3.sup.-) and trap it with electrophiles were unsuccessful. See for example, Hine, J. Physical Organic Chemistry, McGraw-Hill, New York, 1962, p 486; Haszeldine, R. N. J. Chem. Soc. 1954, 1273; Pierce, O. R., McBee, E. T. ; Judd, G. F. J. Am. Chem. Soc. 9154, 76, 474; Bergman, E. J. Org. Chem. 1958, 23, 476.; McBee, E. T., Battershell, R. D., Braendlin, H. P. J. Org. Chem. 1963, 28, 1131. This was thought to be due to the rapid dissociation of CF.sub.3.sup.- into F.sup.- and CF.sub.2. Only recently reports have appeared describing the formal transfer of CF.sub.3.sup.- to organic electrophiles in high yield. See Matsui, K., Tobita, E., Ando, M., Kondo, K. Chem. Lett. 1981, 1719; Ruppert, I., Schlich, K., Volbach, W., Tetrahedron Lett. 1984, 25, 2195; Burger, H., Grunwald, M., Pawelke, G. J. Fluorine Chem. 1986, 31, 89; Wakselman, C., Tordeaux, M. Bull. Soc. Chim. Fr. 1986, 868; Francese, C., Tordeux, M., Wakselman, C. J. Chem. Soc., Chem. Commun. 1987, 642; Francese, C., Tordeux, M., Kitazume, T., Ishikawa, N. J. Am. Chem. Soc. 1985, 107, 5186; Burton, D. J., Wiemers, D. M. J. Am. Chem. Soc. 1985, 107, 5014; Wiemers, D. M., Burton, D. J., J. Am. Chem. Soc. 1986, 108, 832.
Perfluoroalkyl aromatic compounds such as benzotrifluoride, 4-chlorobenzotrifluoride and 3-aminobenzotrifluoride are used in the production of a variety of products such as pharmaceuticals, crop protection chemicals, germicides, dyes, and the like. The classical method of forming trifluoromethyl aromatics involves the photochemical side-chain chlorination of a methyl aromatic compound to form a perchloromethyl substituted aromatic which in turn is reacted with hydrogen fluoride to effect an exchange of fluorine atoms for the chlorine atoms on the methyl group. Ortho- and para-trifluoromethylphenols and anilines are even more difficult to make. They have been synthesized by photochemical side-chain chlorination or bromination of the appropriate nitrotoluene to form the perhalomethyl nitrobenzene. This product is treated with hydrogen fluoride to form the perfluoromethyl nitrobenzene, which is then reduced to the perfluoromethyl aniline. Diazotization and hydrolysis of the latter forms the perfluoromethyl phenol.
In U.S. Pat. No. 4,634,787, Wang reports that reaction between trichloromethyltrimethylsilane and various carbonyl compounds using tetrabutylammonium fluoride as catalyst yielded trichloromethylated compounds as the product of the reaction. While the patentee refers to compounds having a --CX.sub.3 group in which each X is independently halo, according to the patentee:
". . . preferably, each X is independently chloro or bromo. More preferably, each X is the same and is chloro or bromo. Even more preferably, each X is chloro. Preferred silanes [used as reactants in the process] are trichloromethylsilanes and the most preferred silane is trichloromethyltrimethylsilane."
The catalysts recommended by Wang for use in his process are KF, NaF, CaF.sub.2 and Bu.sub.4 NF, the latter being his most preferred catalyst. Unfortunately Bu.sub.4 NF is very expensive and difficult, if not impossible, to dry completely.